NPL 1 describes an example of a conventional packet transmission system. A conventional packet transmission system illustrated in FIG. 15 is constituted by a network node 7-A, a network node 7-B, a network node 7-C, and a network 3 which connects these network nodes. In this example, for convenience of explanation, the number of network nodes is three. The number of network nodes, however, is not limited to the above. Further, the network node 7-A, the network node 7-B, and the network node 7-C communicate with one another via the network 3.
Next, a configuration of the network node 7-A is described using FIG. 15. The other configurations of the network node 7-B and the network node 7-C are the same as the configuration of the network node 7-A. The network node 7-A includes a packet output application 71, a packet aggregation que 72, a packet aggregation unit 73, a memory 74, and a packet receiving unit 75. The packet output application 71 outputs a packet. The packet aggregation que 72 stores a packet to be transmitted to the network 3. The packet aggregation unit 73 aggregates a plurality of packets stored in the packet aggregation que 72 for transmission to the network 3. The memory 74 holds an operation parameter of the packet aggregation unit 73. The packet receiving unit 75 receives a packet from the network 3, and transfers the received packet to the packet output application 71. The packet aggregation unit 73 includes a timer 731 which detects a timeout that gives a trigger for use in transmitting aggregated packets. The memory 74 holds a minimum aggregation number 741 indicating a minimum value of the number of packets aggregated, and a timeout value 742 indicating a timeout value of packet aggregation. Further, a packet 721 is a leading packet of the packet aggregation que 72, and packets 722 are packets whose destinations are the same as the destination of the packet 721.
An operation of the conventional packet transmission system having the aforementioned configuration is described using FIG. 16. In this example, an operation for transmitting packets to the network 3 by the packet output application 71 held in the network node 7-A is described.
Packets output by the packet output application 71 are stored in the packet aggregation que 72. The packet aggregation unit 73 refers to the packet aggregation que 72 and generates, when the packet 721 (indicated by a packet P in FIG. 16) exists at the leading position of the que, at the same time, when the number of the packets 722 (indicated by packets P′ in FIG. 16), whose destinations are the same as the packet 721 stored in the packet aggregation que 72, is larger than the minimum aggregation number 741 (Step F101), a packet aggregating the packet 721 and the packets 722 (Step F102). In this example, the number of the packets 722 (packets P′) to be aggregated into an aggregated packet is equal to the whole number of the packets 722, or is equal to a maximum value of the aggregation number to be allowed by a maximum packet length.
Next, the packet aggregation unit 73 refers to the packet aggregation que 72 and generates, when the packet 721 exists at the leading position of the que, and when the timer 731 set to the timeout value 742 times out (Step F103), a packet aggregating the packet 721 and the packets 722 (Step F104).
In this example, the number of the packets 422 to be aggregated into an aggregated packet is equal to the number of packets aggregated in Step F102.
Next, when an aggregated packet is generated in Step F102 or in Step F104, the packet aggregation unit 73 transmits the generated packet to the network 3 (Step F105). Next, the packet aggregation unit 73 resets the timeout value of the timer 731 to a value determined by the timeout value 742 (Step F106). Next, the conventional packet transmission system continuously transmits packets output by the packet output application 71 to the network 3 by returning to the operation of Step F101.
By performing the aforementioned operation, the conventional packet transmission system aggregates a plurality of packets for transmission to a network to implement broadband packet transmission. As an example, when the network 3 is a network in conformity with a wireless LAN (Local Area Network) protocol, a time interval at which packets are sequentially transmitted is determined by the network protocol. As a result of the determination, a band in which the packet output application 71 can transmit packets to the network 3 is limited. However, aggregating a plurality of packets for transmission makes it possible to reduce a time interval associated with a span between aggregated packets. This makes it possible to implement broadband packet communication.